The increasing use of computer technology in recent years has created a need for larger-capacity storage devices to hold the multitudes of digital files created and used by people on a daily basis. In addition to an increase in the sheer number of pictures, videos, songs and other types of files used by individuals, these files have become larger in size as quality has improved.
Hard disk drive (HDD) technology has addressed this need for larger, faster and more reliable HDDs by incorporating advances such as multiple disk platters per drive, multiple read/write head interfaces (heads) per drive, redundancy through the use of RAID, the use of abstraction techniques such as Logical Unit Numbers (LUN) and so forth.
When HDDs increase storage by adding multiple disk platters in a drive with a head for each disk surface, there is an increased risk of losing access to the entire drive in the event a single head fails. Even if the entire drive is not rendered inoperable by a head failure and commands can still be issued to the drive, reads and writes corresponding to the failed head will fail. Because of serpentine formatting, it is not feasible for a host device to keep using the Logical Block Addresses (LBA) corresponding to the working heads, and ignore the others. This becomes especially problematic as the number of heads per drive increases, because a user may want to continue using the portion of the HDD that is theoretically functional.